The goal of most ceramic forming processes is to create a green body that is as homogeneous as possible, so that the structure will be very uniform after sintering. It is well known that even minor inhomogeneities in the green body can lead to stresses, distortions, and poor mechanical properties (even fracture) of the object after sintering. For example, during slip casting the movement of water from the liquid slurry into the porous mold creates small nonuniformities in the green density of the component and can lead to residual stresses after firing. One of the major benefits of the ceramic gelcasting process is that a uniform slurry is created and poured into a mold, where gelation of the liquid vehicle locks the constituent powder particles into place before settling, floatation, flocculation, or other source of inhomogeneities can operate.
On the other hand, there are many applications in which it is desirable to have a dense ceramic and/or metal component in which the properties vary in some way throughout the article. It may be desirable to produce an article characterized by high hardness on one surface and high toughness in the interior, for example. Particularly for uses involving microwave energy, it is often desirable to have the loss tangent and dielectric constant of an article vary so that microwave energy can be effectively absorbed by the article while minimizing reflections.